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Re: mail basics on a debian system

On Tue, Dec 10, 2002 at 09:49:41PM +0100, Robert Land wrote:
> On Tue, Dec 10, 2002 at 02:02:10PM -0500, Derrick 'dman' Hudson wrote:
> > On Tue, Dec 10, 2002 at 01:56:08PM +0100, Robert Land wrote:
> > | What I'm realy unsure about is if _all_ mail, even the one
> > | sent by the lowlevel 'mail' program goes through port 25.
> > 
> > No.  Many unix programs use a local pipe to deliver mail (eg mail,
> > mutt, cron and others).
> Is this what "batched smtp" refers to?

Batched SMTP is a slightly more specialized technique, used when you're
getting a group of messages from some source other than normal SMTP and
injecting them into the mail system all at once. The basic idea is that
you save (i.e. "batch") the transaction that would normally happen on
port 25 to a file, and replay it later. I use this for list mail so that
the friend who runs the server where my mail normally goes doesn't have
to deal with the 500 messages a day from all my Debian list
subscriptions; it amounts to sshing to another machine, grabbing a file,
and calling '/usr/sbin/sendmail -bS' with that file on standard input.

Derrick's referring, I think, to calling /usr/sbin/sendmail with a
single message on standard input.

At any rate, all three of these mechanisms (TCP connection to port 25,
BSMTP, plain sendmail) go through your local mail transport agent, as
does any other normal means of sending mail in Unix.

Colin Watson                                  [cjwatson@flatline.org.uk]

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